This invention relates to the charging of coke ovens, and more particularly, it relates to the removal of gases generated during the charging of single-main coke ovens, in which the charging hole of the coke oven and the interior of the coke chamber are substantially blocked by the column of incoming coal.
During the charging of coal into single-main coke ovens, a temporary increase, or surge, occurs in the volume of gases. This surge is due to the physical displacement of the furnace gases as the coal fills the coking chamber, and due to the evolution of additional gases due to the volatilization of coal. The term charging gases refers to the total volume of gases generated by displacement and by evolution. The oven aspiration system must exhaust these charging gases.
If these charging gases are not removed, the gas pressure builds up in the oven and emission of gas can occur at the nearest portals, such as the coke oven doors and charge holes which are not being used, and therefore, pollution of the amosphere can result.
In a typical coke chamber, substantially all of the charging gases must be removed via the free gas-flow area above the charged coal. The cross-sectional area of this gas-flow area determines the gas velocity, the gas pressures and eventually the emissions to a considerable degree. A greater free gas-flow area permits a lower gas velocity for a given effective gas removal, and makes it easier for the oven aspiration system to remove the charging gases.
However, as the oven fills, the free space cross-sectional area of the gas flow decreases, and the charging gas volume increases. During the time when the free cross-sectional area is decreasing, and the charging gas volume is greatly increasing, it is necessary for the existing aspiration system to provide maximum gas velocity to remove the charging gas from the oven in order to prevent gas emission. Otherwise the gas can seep out into the atmosphere.
However, maximum gas velocity in the gas-flow area tends to vacuum out of the oven and into the aspiration system considerable amounts of fine coal. Build-up of this coal in the aspiration system makes subsequent aspiration even more difficult.
Also, for many single-main coke ovens, the interior width of the chamber is substantially filled by the column of falling coal, and all of the charging gas on the side of the oven away from the collecting main cannot, therefore, pass between the chamber wall and the coal column. Because of its inability to flow to the collecting main, a portion of the charging gas gets trapped in the coking chamber, and builds up pressure, and eventually seeps out into the atmosphere.
The coal falling into the ovens falls as a columnar mass whose horizontal cross-sectional dimensions are controlled by the minimum horizontal cross-sectional dimensions of the charging hole. In the ovens to which this invention relates, the minimum dimensions of the charging hole are the same as the corresponding minimum dimensions of the collar and bottom discharge opening of the larry car hopper feeding the oven, and the column of in-coming coal substantially blocks the interior width of the coking chamber.